package com.TT.ticket.rw;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * 独占锁（写锁） 一次只能被一个线程占有
 * 共享锁（读锁） 多个线程可以同时占有
 * ReadWriteLock
 *
 * 读-读 可以共存
 * 读-写 不能共存
 * 写-写 不能共存
 *
 */
public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCache myCache = new MyCache();

        for (int i = 1; i <= 5; i++) {


            final int temp = i;

            new Thread(() -> {
                myCache.put(temp + "", temp + "");
            }, String.valueOf(i)).start();

        }


        for (int i = 1; i <= 5; i++) {


            final int temp = i;

            new Thread(() -> {
                myCache.get(temp + "");
            }, String.valueOf(i)).start();

        }
    }
}


class MyCache {
    private volatile Map<String, Object> map = new HashMap<>();
    //读写锁 更加细粒度的控制
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();


    //存，写入时候，只希望同时只有一个线程写
    public void put(String key, Object value) {
        readWriteLock.writeLock().lock();

        try {
            System.out.println(Thread.currentThread().getName() + "写入" + key);
            map.put(key, value);
            System.out.println(Thread.currentThread().getName() + "写入ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.writeLock().unlock();
        }
    }

    //取，读，所有人都可以读
    public void get(String key) {
        readWriteLock.readLock().lock();

        try {
            System.out.println(Thread.currentThread().getName() + "读取" + key);
            map.get(key);
            System.out.println(Thread.currentThread().getName() + "读取ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.readLock().unlock();
        }
    }

}